Modern automobiles utilize a number of microprocessor-controlled modules to provide a variety of functions within the automobile. These modules provide both control and diagnostic function. Examples of such control modules are the modules that manage the seat functions and store the memorized seat configurations for particular occupants. Other modules are responsible for climate control, traction control, airbag deployment, radio, etc. A typical automobile may have as few as 4 or more than 40 modules. These modules are placed in various locations throughout the vehicle.
These modules communicate with each other over a serial data bus that connects all of the modules together. This bus also connects to the diagnostic connector, which is typically located under the dashboard of the vehicle. Problems with the modules are normally diagnosed by connecting a diagnostic computer to the diagnostic connector by using a standardized connector. The diagnostic computer then queries the modules to determine if the modules are functioning properly using programs that are provided for each make and model of vehicle.
This diagnostic system depends on the serial bus functioning properly. Unfortunately, modules are known to fail in a manner that either shorts the bus signal conductor to ground or to power. In the event of such a failure, none of the functioning modules can communicate over the bus. Similarly, a short in the communication line itself can lead to a similar problem.
If the bus is not functioning, the diagnostic computer cannot provide sufficient information to isolate the problem. In such situations, the technician is often reduced to disconnecting modules one at a time until the technician finds the module that is interfering with the bus. The modules in question are located at a number of locations on the vehicle. Many of these locations require a significant amount of labor to access. For example, a module located in the recesses of the dashboard may require that the dashboard be removed before the module can be accessed. Accordingly, the cost of servicing the vehicle when such a fault occurs can be substantial.
Techniques for avoiding this type of problem are known in the computer network arts. However, such techniques are poorly suited to the automobile environment, which places limitations on the cost of the protection, and the environment in which the network protection components must operate. In addition, a failure in the protection circuitry itself can lead to data losses that pose a safety hazard when the data is critical to the operation of a moving vehicle. Hence, automobile manufacturers have not utilized this solution.
In addition, there is a considerable investment in test equipment such as the diagnostic computers discussed above. Hence, any solution to this problem that involves changing the currently used diagnostic system can be prohibitively expensive. In addition, any change in the diagnostic procedures presents additional staff training costs, and hence, any solution to these problems needs to minimize the number of changes in the established procedures.